Consciousness is originally pure, like water. But if we mix water with a certain color, it changes. Similarly, consciousness is pure, for the spirit soul is pure. But consciousness is changed according to the association of the material qualities.
Bhagavad-gita 15.9,
Srila Prabhupada

Water is very clean. When it rains from the clouds it is very clean, but as soon as it drops on the ground it becomes muddy. So that muddiness has to be cleansed then water will come out again clean. Similarly, our consciousness is clean, but because it is contaminated with the muddy things of the material nature, it is cloudy.